I read the "22 Immutable Laws of Marketing" many many years ago, and it repeatedly spells out the folly of large companies who became huge on the back of just ONE product then thinking that they needed to have alternatives or provide more choice and broadened their range to the overall long term detriment of the main product or business that made them huge in the first place.
EDIT: Just to clarify - it is not just Stripe Press. I am including initiatives like acquiring the Indie Hackers site (which I enjoy BTW) a while back etc. I can totally see that these are all related to Stripe's audience of tech startups, but it still has the ring of, say, a candy company who starts diversifying into a clothing line etc.
End of the day - every employee who is distracted by looking after the assets & numbers for these side projects is an employee who is not focused on their core payments system.